Cardinalfish (Apogonidae) is a speciose family of marine teleosts with about 23 genera and 347 valid species, of which most occur in shallow water in tropical and subtropical marine environments and a few species occur in brackish and fresh water environments (Nelson, Reference Nelson2006; Fraser & Allen, Reference Fraser and Allen2010). Apogonid fish are usually small in size (<100 mm total length) but a few species in the genera Apogon, Holapogon, Apogonichthyoides, Cheilodipterus, Glossamia and Pseudamia grow to larger sizes (Fraser, Reference Fraser1973; Froese & Pauly, Reference Froese and Pauly2011).
The genus Apogonichthyoides, which was resurrected from Apogon, contains 19 valid species (Fraser & Allen, Reference Fraser and Allen2010). The characteristics of the genus are: body colour brown to brownish-black; head and body usually with dark (brown or black) spots which are sometimes stripe-like; a dark cheek line and usually two body bars. An ocellus may be present below the lateral line on the body; one or more bars on the caudal peduncle or a spot on the base of the caudal fin are often present (Fraser & Allen, Reference Fraser and Allen2010).
Species of the ‘Apogonichthyoides nigripinnis’ complex have a similar colour pattern with a dark colour and a spot on the caudal peduncle. The species known from the western Indian Ocean ‘A. nigripinnis’ group are A. enigmaticus, A. heptastygma, A. pharaonis, A. pseudotaeniatus, A. taeniatus and A. nigripinnis from the Indo-West Pacific (Fraser & Allen, Reference Fraser and Allen2010; Froese & Pauly, Reference Froese and Pauly2011).
Apogonichthyoides sialis (Jordan & Thompson, Reference Jordan and Thompson1914), originally described as Amia sialis from Suruga Bay (Japan) is distributed from the western Pacific (including Japan, Taiwan and China) to the east coast of India (Gon, Reference Gon2000). On 3 August 2011 five specimens of A. sialis were collected from demersal fish trawl landings at Munambam Fisheries Harbour, south-western India. The main part of the catch comprised Nemipterus randalli and N. japonicus. The morphometric and meristic characters of the specimens collected agree well with the description of Gon (Reference Gon2000), but a few characteristics overlapped with the present specimens which were: colour variants, probably due to habitat; dark colour of the dorsal, anal and caudal fins versus paler in the living photographs of A. sialis. The present work extends the distribution of A. sialis to the west coast of India.
MATERIALS EXAMINED
Apogonichthyoides sialis (DNR CMFRI. GB. 31. 9. 2. 1), (5 specimens, 89.4–102.8 mm standard length), trawls, off Cochin, Kerala, India, 20–70 m depth.
DIAGNOSIS
Dorsal fin rays VII + I, 9; anal fin rays II, 8; pectoral fin rays 15–16; lateral-line scales 23–24 + 2–4; predorsal scales 4, dorsal origin to LL 3 scales. Rudiments and gill-rakers 3 + 2 – 8–9 + 4–6, 10–11 rakers, total 5 + 12–15; two dark body bars from base of each dorsal fin; small basicaudal spot.
DESCRIPTION
Proportional measurements in percentage of standard length (SL) are given (Tables 1 & 2). A medium sized Apogon, with dark colour and very small spots and a black spot on caudal (Figure 1). Body depth 2.3–2.4 in SL; head length (HL) 41.9–45% SL, 2.2–2.4 in SL; snout length 4.1–4.5 in HL; upper jaw length 19.2–19.7% SL; third dorsal-fin spine 22.3–23.6% SL; second dorsal spine 18.7–20.4% SL; pelvic-fin spine 15.6–18.0% SL; caudal peduncle depth (CPD) 16.1–17.5% SL; caudal peduncle length (CPL) 19.5–24.8% SL, 4–5.6 in SL; caudal spot diameter 4.8–5.6% SL. Eye diameter 3.5–3.9; interorbital 4.2–4.7; upper jaw 2.1–2.4; third dorsal spine 1.8–2.0; second anal spine 4.6–6.1; pelvic spine 2.4–2.9, all in HL (Tables 1 & 2). Preoperculum finely serrated. Pelvic bases connected by a membrane (interpelvic space covered). Large mouth, villiform teeth. Pectoral fin nearly reaches to anal fin origin in vertical. Caudal fin emarginate.
COLOUR
Colour in alcohol: body grey-brown with minute small dark spots and with two distinct dark bars, one under anterior base of each dorsal fin; intestine pale.
Colour of fresh specimens: body dark; dark bars from dorsal to ventral side, reaching to level of lower pectoral-fin base or slightly lower; a distinct dark caudal spot.
REMARKS
A similar species from western Indian Ocean, A. pseudotaeniatus (Gon, Reference Gon1986) described from the Red Sea can be confused with A. sialis in colour pattern and morphometry, except for a few characters such as: third dorsal spine 1.9–2 in HL (2.0–2.45 in A. pseudotaeniatus) and smaller dark basicaudal spot, spot diameter 3.5–5.2 in CPD (4.6–6.1 in A. pseudotaeniatus). Moreover A. pseudotaeniatus has a blackish intestine and usually 14–15 pectoral fin rays, whereas A. sialis has a pale intestine and usually 15 pectoral fin rays.
Day's (Reference Day1875) Fishes of India, plate 16 figure 9 misidentified as A. bifasciatus is A. sialis. There are no specimens of A. pseudotaeniatus reported from the eastern Indian coastline, but Gon (Reference Gon1986) suggested Day's (Reference Day1875) report of A. taeniatus was A. pseudotaeniatus with abnormality which could be A. sialis. Apogonichthyoides pseudotaeniatus is probably restricted to the Red Sea, Arabian coast and the Persian Gulf and prefers reefs found at 5–30 m depth (Gon & Randall, Reference Gon and Randall2003), whereas present A. sialis specimens were collected from the south-western coast of India, 20–70 m depth. Suresh & Thomas (Reference Suresh and Thomas2006) reported A. pseudotaeniatus from the west coast of India which also could be A. sialis. This report of A. sialis from the south-western coast of India indicates an extension of distribution from its known localities.
ACKNOWLEDGEMENTS
The authors are grateful to the Director, CMFRI for the support and encouragement. Our sincere thanks to Dr Thomas H. Fraser, Florida Museum of Natural History, USA, for sending valuable publications required for preparation of manuscript and all support. We would also like to thank the referee for helpful comments on the manuscript.